Gravity davit



H. G. TAYLOR GRAVITY DAVIT March 24, 1953 Filed .Nov. 27, 1950 INVENTOR HUMPHREY GEORGE TAYLCI ATTORNEY Patented Mar. 24, 1953 UNITED PTENT OFFECE GRAVITY DAVIT Application November 2'1, 1950, Serial No. 197,677 In Great Britain November 30, 1948 2 Claims.

The invention relates to gravity davits in which each davit arm is widened at its foot and formed, at its under side, as a convex curve arranged to roll on a track which is substantially horizontal but may be of slightly convex form. A plain horizontal track is, however, preferred. When the davit arm is inboard the inner end or heel of the foot of the davit arm rests on the track and is positioned somewhat inboard of the point on the davit arm from which the boat is hung. On the falls being released, the arm swings outwardly the curved-under surface of its foot rolling on the track until the toe of the foot rests on the track when the davit arm reaches the extreme outboard position.

While the foot is rolling on the track there may be a tendency for its under surface to slip back in relation to the track; and, to prevent this, teeth have been formed on the under surface of the foot to engage with teeth formed on the track. Means other than teeth have been used to prevent slipping back, for example ropes anchored one at the heel and one at the toe, the former passing forward and the latter backward each anchored to the frame. It is also known to incline the track steeply in a downward and outward direction.

According to this invention, in lieu of forming teeth on the foot and track, these are left plain and a laterally projecting pin or roller is provided at one or each side of the heel of the foot, the, or each, pin or roller engaging back against a curved rear track so shaped that as the arm swings outboard the under surface of its foot can roll freely on the bottom track but is prevented, throughout almost throughout its travel, from slipping back in relation thereto.

Each pin or roller, when it reaches the upper end of the rear track, may encounter a stop to limit the outboard movement of the arm.

If the main track is straight, and if the curve of the under side of the foot forms a part of a circle, then the curve of the rear track is cycloidal.

In order to prevent or limit slipping of the foot on the bottom track as the davit arm is moved inboard, a pin or roller may be provided at one or each side of the toe of the foot adapted to engage forwardly against a forward track, or one of a pair of forward tracks, which is or may be the counterpart of the said rear track.

Any suitable means may be provided to limit the inboard movement of the davit arm, for instance a stop at the upper end of the forward track, or simply a fixed stop positioned behind the davit arm.

The forward and rear tracks may be formed in two vertical fixed plates, one at each side of the lower part or foot of the davit arm, by forming curved slots in each plate, or by forming a recess or cut-out in each of the plates, two edges of the recess or cut-out forming the tracks.

An embodiment of the invention is shown, by way of example, in the accompanying drawings; in which:

Figs. 1 and 2 are respectively a side elevation and an inboard view of the gravity davit.

Referring to the drawings, the davit arm I has a widened foot portion 2 with a convex underside 3 arranged to roll or rock upon a fixed track 4 on the base or deck frame 5, said track 4 being horizontally disposed although it may be slightly inclined downwardly in either an inboard or outboard direction and, it may, instead of being fiat, be of a slightly convex form in the direction of its length. The upper surface of the fixed track 4 is plain, that is to say without teeth.

When the davit arm I is inboard, as shown in full lines in Fig. 1, the inner end or heel of the foot 2 rests on the track 4 at a position somewhat inboard of that point on the davit arm I from which the ships boat 6 is hung. On the falls 1 being released or paid out, the davit arm swings outwardly automatically, the curved under surface 3 of its foot rolling, in the manner of a rocker, outwardly on the track 4 until the toe end of the foot 2 rests on the track 4 when the davit arm I reaches the outboard position shown in chain lines in Fig. 1.

During this rolling or rocking movement of the davit arm foot 2 on the track 4 there is a tendency of the foot to slip back in relation to the track. This is prevented by trunnion pins or rollers I which project laterally from opposite sides of the heel of the foot 2 and each of which engages back against a curved track 8. These curved tracks 8 are afforded by the outwardly presented edges of cut-outs in vertically disposed plates 9 which flank the opposite sides of the davit arm I and constitute side walls of the deck frame of the davit.

When the pins or rollers 1 reach the upper end of the curved tracks 8 they encounter stops afforded by the rear portions of the upper edges H) of the cut-outs in the plates 9, as shown in chain lines in Fig. 1, so as to limit the outboard movement of the davit arm I.

Similarly during the inboard swinging movement of the davit arm I, any tendency for the foot 2 to slide forwardly on the track 4 is prevented or limited by inwardly presented curved track edges ll of the cut-outs in the plates 9 being engaged by trunnion pins or rollers 12 which project laterally from opposite sides of the toe of the foot 2.

At the extreme end of the inboard swinging movement of the davit arm I the foot rocks on to its heel which has a small radius as compared with the main rocker surface 3. Consequently there is introduced into the movement of the rollers I an increased horizontal component, and this is provided for by shallow notches 3 at the lower ends of the tracks 8. Similarly shallow notches [4 at the lower ends of the tracks I! accommodate the increased horizontal component of the movement of the rollers [2 as the foot 2 rocks on to its toe at the end of the outboard swinging movement of the davit arm I.

The inboard swinging movement is determined by the pins or rollers I2 coming against the forward portions of the upper edges of the cut-outs in the plates 9.

Obviously, instead of providing cut-outs which afford the controlling tracks for the swinging movements of the davit arm, such tracks may be afforded by separate curved slots in the plates 8 the upper ends of these slots being engaged by the heel and toe pins or rollers respectively to determine the swinging movements of the davit arm.

Having fully described my invention, what I claim and desire to secure by Letters Patent is:

1 A gravity operated davit comprising a track for mounting in a substantially horizontal position on a ship, an upstanding frame extending from said track and fixedly secured thereto and having a central opening with the upwardly extending edges of the opening forming curved cam surfaces and the lower ends of the upwardly extending edges of the opening forming shallow notches, a davit arm having a curved rocker at its lower end mounted for rocking movement on said track with the radius of curvature of the rocker being smaller at the inboard and outboard ends thereof than at the intermediate portion thereof, trunnions at the inboard and outboard ends of said rocker for engagement with said curved cam surfaces for maintaining the rocker in engagement with the track, the position of the trunnions, cam surfaces, notches, and the radii of curvature of said rocker being such that the trunnions extend into said notches in the extreme inboard and outboard position of said davit arm, the davit arm projecting above the rocker when the rocker is in its inboard position, the load supporting end of the davit arm being outboard of the point of engagement of said rocker with said track whereby a load urges the davit to its outboard position.

2. A gravity operated davit comprising a track for mounting in a substantially horizontal position on a ship, an upstanding frame extending from said track and fixedly secured thereto and having a central opening with the upwardly extending edges of the opening forming curved cam surfaces and the lower ends of the upwardly extending edges of the opening forming shallow notches, a davit arm having a curved rocker at its lower end mounted for rocking movement on said track with the radius of curvature, of the rocker being smaller at the inboard and outboard ends thereof than at the intermediate portion thereof, said davit arm and rocker being in substantially the plane of the track, trunnions at the inboard and outboard ends of said rocker for engagement with said curved cam surfaces for maintaining the rocker in engagement with the track, the position of the trunnions, cam surfaces, notches, and the radii of curvature of said rocker being such that the trunnions extend into said notches in the extreme inboard and outboard position of said davit arm, the davit arm projecting above the rocker when the rocker is in its inboard position, the load supporting end of the davit arm being outboard of the point of engagement of said rocker with said track whereby a load urges the davit to its outboard position.

HUMPHREY G. TAYLOR.

REFERENCES CITED The following references are of record in the file of this patent:

FOREIGN PATENTS Number Country Date 10,442 Great Britain 1911 17,778 Great Britain 1914 946,014 France Dec. 6, 1948 

